A fastener element made of metal (hereinafter, may simply be called a metallic element) generally includes a coupling head, a body extending backward from a base end portion of the coupling head, and a pair of left and right leg portions extending backward after being bifurcated from the body. Such a metallic element is manufactured by two representative methods described below.
According to a first manufacturing method of a metallic element, a coupling head or the like is molded by plastic deformation of a rectangular wire material made of metal with a pressing force and the molded rectangular wire material is punched or cut into an element shape using a punch, die or the like to manufacture each fastener element in a scattered state.
Fastener elements obtained as described above undergo a polishing process such as barrel polishing or chemical polishing and a coating process that applies a clear coating to the element surface and then, one fastener element after another is planted to one side edge portion of a fastener tape at predetermined intervals using a caulking means. Accordingly, a fastener stringer in which a plurality of metallic elements is attached to the fastener tape in a row is manufactured successively.
An example of the method of manufacturing metallic elements from a rectangular wire material as described above is disclosed by U.S. Pat. No. 2,116,712 (Patent Document 1). Particularly, according to the manufacturing method described in Patent Document 1, before a coupling head or the like is molded, a pressing force is applied to left and right edge portions along the longitudinal direction of a rectangular wire material by the rectangular wire material being passed between a pair of rollers. Accordingly, square left and right side edge portions of a rectangular wire material are rounded to form a smooth surface.
A coupling head or the like is molded by applying a pressing force to a wire made of metal whose left and right side edge portions are rounded and then the wire is cut by a cutting die into an element shape and also a leg portion is extended in the width direction by punching. Accordingly, as shown in FIG. 7, a metallic element 50 whose outer edge portions on left and right sides on first and second surface sides (lower and upper surface sides) of a coupling head 51 and leg portions 52 are rounded is manufactured.
According to Patent Document 1, by configuring a slide fastener using the metallic element 50 described above, outer edge portions of the metallic element 50 are smooth and so the slider can be slidingly moved more easily and also the noise produced while the slider is slidingly moved can be reduced.
On the other hand, according to a second manufacturing method of a metallic element, a long metallic wire having a circular cross section is first passed through a plurality of pressure rolls to mold the wire so as to have a transverse section in a substantial Y shape and the molded wire (so-called Y bar) is successively cut with a desired thickness in the length direction using a cutting punch and a cutting die to successively produce an element component. Subsequently, a portion corresponding to a coupling head of the obtained element component is locally deformed by applying a pressing force to mold a coupling convex portion and a coupling concave portion to manufacture a metallic element.
Subsequent to the molding of the coupling convex portion and the coupling concave portion, metallic elements obtained as described above are planted to one side edge portion of a fastener tape transferred separately from the metallic elements one by one using a caulking means (caulking punch) to manufacture a fastener stringer.    Patent Document 1: U.S. Pat. No. 2,116,712